bcachefs: Fix interior update path btree_path uses

Since the btree_paths array is now about to become growable, we have to
be careful not to refer to paths by pointer across contexts where they
may be reallocated.

This fixes the remaining btree_interior_update() paths - split and
merge.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

3 files changed, 51 insertions, 43 deletions

diff --git a/fs/bcachefs/btree_trans_commit.c b/fs/bcachefs/btree_trans_commit.c
index 7e6ba3061e7c..2ec9ff06f1a6 100644
--- a/fs/bcachefs/btree_trans_commit.c
+++ b/fs/bcachefs/btree_trans_commit.c
@@ -823,7 +823,7 @@ static inline int do_bch2_trans_commit(struct btree_trans *trans, unsigned flags
 
 		if (!same_leaf_as_next(trans, i)) {
 			if (u64s_delta <= 0) {
-				ret = bch2_foreground_maybe_merge(trans, trans->paths + i->path,
+				ret = bch2_foreground_maybe_merge(trans, i->path,
 							i->level, flags);
 				if (unlikely(ret))
 					return ret;
@@ -877,14 +877,12 @@ int bch2_trans_commit_error(struct btree_trans *trans, unsigned flags,
 	struct bch_fs *c = trans->c;
 
 	switch (ret) {
-	case -BCH_ERR_btree_insert_btree_node_full: {
-		struct btree_path *path = trans->paths + i->path;
-
-		ret = bch2_btree_split_leaf(trans, path, flags);
+	case -BCH_ERR_btree_insert_btree_node_full:
+		ret = bch2_btree_split_leaf(trans, i->path, flags);
 		if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
-			trace_and_count(c, trans_restart_btree_node_split, trans, trace_ip, path);
+			trace_and_count(c, trans_restart_btree_node_split, trans,
+					trace_ip, trans->paths + i->path);
 		break;
-	}
 	case -BCH_ERR_btree_insert_need_mark_replicas:
 		ret = drop_locks_do(trans,
 			bch2_replicas_delta_list_mark(c, trans->fs_usage_deltas));
diff --git a/fs/bcachefs/btree_update_interior.c b/fs/bcachefs/btree_update_interior.c
index 737ccbe1aef9..2a93eb92d112 100644
--- a/fs/bcachefs/btree_update_interior.c
+++ b/fs/bcachefs/btree_update_interior.c
@@ -25,7 +25,7 @@
 #include <linux/random.h>
 
 static int bch2_btree_insert_node(struct btree_update *, struct btree_trans *,
-				  struct btree_path *, struct btree *,
+				  btree_path_idx_t, struct btree *,
 				  struct keylist *, unsigned);
 static void bch2_btree_update_add_new_node(struct btree_update *, struct btree *);
 
@@ -1454,10 +1454,12 @@ static void __btree_split_node(struct btree_update *as,
  */
 static void btree_split_insert_keys(struct btree_update *as,
 				    struct btree_trans *trans,
-				    struct btree_path *path,
+				    btree_path_idx_t path_idx,
 				    struct btree *b,
 				    struct keylist *keys)
 {
+	struct btree_path *path = trans->paths + path_idx;
+
 	if (!bch2_keylist_empty(keys) &&
 	    bpos_le(bch2_keylist_front(keys)->k.p, b->data->max_key)) {
 		struct btree_node_iter node_iter;
@@ -1471,18 +1473,18 @@ static void btree_split_insert_keys(struct btree_update *as,
 }
 
 static int btree_split(struct btree_update *as, struct btree_trans *trans,
-		       struct btree_path *path, struct btree *b,
+		       btree_path_idx_t path, struct btree *b,
 		       struct keylist *keys, unsigned flags)
 {
 	struct bch_fs *c = as->c;
-	struct btree *parent = btree_node_parent(path, b);
+	struct btree *parent = btree_node_parent(trans->paths + path, b);
 	struct btree *n1, *n2 = NULL, *n3 = NULL;
 	btree_path_idx_t path1 = 0, path2 = 0;
 	u64 start_time = local_clock();
 	int ret = 0;
 
 	BUG_ON(!parent && (b != btree_node_root(c, b)));
-	BUG_ON(parent && !btree_node_intent_locked(path, b->c.level + 1));
+	BUG_ON(parent && !btree_node_intent_locked(trans->paths + path, b->c.level + 1));
 
 	bch2_btree_interior_update_will_free_node(as, b);
 
@@ -1510,12 +1512,12 @@ static int btree_split(struct btree_update *as, struct btree_trans *trans,
 		six_unlock_write(&n2->c.lock);
 		six_unlock_write(&n1->c.lock);
 
-		path1 = get_unlocked_mut_path(trans, path->btree_id, n1->c.level, n1->key.k.p);
+		path1 = get_unlocked_mut_path(trans, as->btree_id, n1->c.level, n1->key.k.p);
 		six_lock_increment(&n1->c.lock, SIX_LOCK_intent);
 		mark_btree_node_locked(trans, trans->paths + path1, n1->c.level, BTREE_NODE_INTENT_LOCKED);
 		bch2_btree_path_level_init(trans, trans->paths + path1, n1);
 
-		path2 = get_unlocked_mut_path(trans, path->btree_id, n2->c.level, n2->key.k.p);
+		path2 = get_unlocked_mut_path(trans, as->btree_id, n2->c.level, n2->key.k.p);
 		six_lock_increment(&n2->c.lock, SIX_LOCK_intent);
 		mark_btree_node_locked(trans, trans->paths + path2, n2->c.level, BTREE_NODE_INTENT_LOCKED);
 		bch2_btree_path_level_init(trans, trans->paths + path2, n2);
@@ -1560,7 +1562,7 @@ static int btree_split(struct btree_update *as, struct btree_trans *trans,
 		bch2_btree_update_add_new_node(as, n1);
 		six_unlock_write(&n1->c.lock);
 
-		path1 = get_unlocked_mut_path(trans, path->btree_id, n1->c.level, n1->key.k.p);
+		path1 = get_unlocked_mut_path(trans, as->btree_id, n1->c.level, n1->key.k.p);
 		six_lock_increment(&n1->c.lock, SIX_LOCK_intent);
 		mark_btree_node_locked(trans, trans->paths + path1, n1->c.level, BTREE_NODE_INTENT_LOCKED);
 		bch2_btree_path_level_init(trans, trans->paths + path1, n1);
@@ -1577,10 +1579,10 @@ static int btree_split(struct btree_update *as, struct btree_trans *trans,
 		if (ret)
 			goto err;
 	} else if (n3) {
-		bch2_btree_set_root(as, trans, path, n3);
+		bch2_btree_set_root(as, trans, trans->paths + path, n3);
 	} else {
 		/* Root filled up but didn't need to be split */
-		bch2_btree_set_root(as, trans, path, n1);
+		bch2_btree_set_root(as, trans, trans->paths + path, n1);
 	}
 
 	if (n3) {
@@ -1600,10 +1602,10 @@ static int btree_split(struct btree_update *as, struct btree_trans *trans,
 	 * node after another thread has locked and updated the new node, thus
 	 * seeing stale data:
 	 */
-	bch2_btree_node_free_inmem(trans, path, b);
+	bch2_btree_node_free_inmem(trans, trans->paths + path, b);
 
 	if (n3)
-		bch2_trans_node_add(trans, path, n3);
+		bch2_trans_node_add(trans, trans->paths + path, n3);
 	if (n2)
 		bch2_trans_node_add(trans, trans->paths + path2, n2);
 	bch2_trans_node_add(trans, trans->paths + path1, n1);
@@ -1665,7 +1667,7 @@ bch2_btree_insert_keys_interior(struct btree_update *as,
  *
  * @as:			btree_update object
  * @trans:		btree_trans object
- * @path:		path that points to current node
+ * @path_idx:		path that points to current node
  * @b:			node to insert keys into
  * @keys:		list of keys to insert
  * @flags:		transaction commit flags
@@ -1677,10 +1679,11 @@ bch2_btree_insert_keys_interior(struct btree_update *as,
  * for leaf nodes -- inserts into interior nodes have to be atomic.
  */
 static int bch2_btree_insert_node(struct btree_update *as, struct btree_trans *trans,
-				  struct btree_path *path, struct btree *b,
+				  btree_path_idx_t path_idx, struct btree *b,
 				  struct keylist *keys, unsigned flags)
 {
 	struct bch_fs *c = as->c;
+	struct btree_path *path = trans->paths + path_idx;
 	int old_u64s = le16_to_cpu(btree_bset_last(b)->u64s);
 	int old_live_u64s = b->nr.live_u64s;
 	int live_u64s_added, u64s_added;
@@ -1733,19 +1736,22 @@ split:
 		return btree_trans_restart(trans, BCH_ERR_transaction_restart_split_race);
 	}
 
-	return btree_split(as, trans, path, b, keys, flags);
+	return btree_split(as, trans, path_idx, b, keys, flags);
 }
 
 int bch2_btree_split_leaf(struct btree_trans *trans,
-			  struct btree_path *path,
+			  btree_path_idx_t path,
 			  unsigned flags)
 {
-	struct btree *b = path_l(path)->b;
+	/* btree_split & merge may both cause paths array to be reallocated */
+
+	struct btree *b = path_l(trans->paths + path)->b;
 	struct btree_update *as;
 	unsigned l;
 	int ret = 0;
 
-	as = bch2_btree_update_start(trans, path, path->level,
+	as = bch2_btree_update_start(trans, trans->paths + path,
+				     trans->paths[path].level,
 				     true, flags);
 	if (IS_ERR(as))
 		return PTR_ERR(as);
@@ -1758,14 +1764,16 @@ int bch2_btree_split_leaf(struct btree_trans *trans,
 
 	bch2_btree_update_done(as, trans);
 
-	for (l = path->level + 1; btree_node_intent_locked(path, l) && !ret; l++)
+	for (l = trans->paths[path].level + 1;
+	     btree_node_intent_locked(&trans->paths[path], l) && !ret;
+	     l++)
 		ret = bch2_foreground_maybe_merge(trans, path, l, flags);
 
 	return ret;
 }
 
 int __bch2_foreground_maybe_merge(struct btree_trans *trans,
-				  struct btree_path *path,
+				  btree_path_idx_t path,
 				  unsigned level,
 				  unsigned flags,
 				  enum btree_node_sibling sib)
@@ -1778,14 +1786,15 @@ int __bch2_foreground_maybe_merge(struct btree_trans *trans,
 	struct btree *b, *m, *n, *prev, *next, *parent;
 	struct bpos sib_pos;
 	size_t sib_u64s;
+	enum btree_id btree = trans->paths[path].btree_id;
 	btree_path_idx_t sib_path = 0, new_path = 0;
 	u64 start_time = local_clock();
 	int ret = 0;
 
-	BUG_ON(!path->should_be_locked);
-	BUG_ON(!btree_node_locked(path, level));
+	BUG_ON(!trans->paths[path].should_be_locked);
+	BUG_ON(!btree_node_locked(&trans->paths[path], level));
 
-	b = path->l[level].b;
+	b = trans->paths[path].l[level].b;
 
 	if ((sib == btree_prev_sib && bpos_eq(b->data->min_key, POS_MIN)) ||
 	    (sib == btree_next_sib && bpos_eq(b->data->max_key, SPOS_MAX))) {
@@ -1797,7 +1806,7 @@ int __bch2_foreground_maybe_merge(struct btree_trans *trans,
 		? bpos_predecessor(b->data->min_key)
 		: bpos_successor(b->data->max_key);
 
-	sib_path = bch2_path_get(trans, path->btree_id, sib_pos,
+	sib_path = bch2_path_get(trans, btree, sib_pos,
 				 U8_MAX, level, BTREE_ITER_INTENT, _THIS_IP_);
 	ret = bch2_btree_path_traverse(trans, sib_path, false);
 	if (ret)
@@ -1807,7 +1816,7 @@ int __bch2_foreground_maybe_merge(struct btree_trans *trans,
 
 	m = trans->paths[sib_path].l[level].b;
 
-	if (btree_node_parent(path, b) !=
+	if (btree_node_parent(trans->paths + path, b) !=
 	    btree_node_parent(trans->paths + sib_path, m)) {
 		b->sib_u64s[sib] = U16_MAX;
 		goto out;
@@ -1861,8 +1870,8 @@ int __bch2_foreground_maybe_merge(struct btree_trans *trans,
 	if (b->sib_u64s[sib] > c->btree_foreground_merge_threshold)
 		goto out;
 
-	parent = btree_node_parent(path, b);
-	as = bch2_btree_update_start(trans, path, level, false,
+	parent = btree_node_parent(trans->paths + path, b);
+	as = bch2_btree_update_start(trans, trans->paths + path, level, false,
 				     BCH_TRANS_COMMIT_no_enospc|flags);
 	ret = PTR_ERR_OR_ZERO(as);
 	if (ret)
@@ -1892,7 +1901,7 @@ int __bch2_foreground_maybe_merge(struct btree_trans *trans,
 	bch2_btree_update_add_new_node(as, n);
 	six_unlock_write(&n->c.lock);
 
-	new_path = get_unlocked_mut_path(trans, path->btree_id, n->c.level, n->key.k.p);
+	new_path = get_unlocked_mut_path(trans, btree, n->c.level, n->key.k.p);
 	six_lock_increment(&n->c.lock, SIX_LOCK_intent);
 	mark_btree_node_locked(trans, trans->paths + new_path, n->c.level, BTREE_NODE_INTENT_LOCKED);
 	bch2_btree_path_level_init(trans, trans->paths + new_path, n);
@@ -1913,10 +1922,10 @@ int __bch2_foreground_maybe_merge(struct btree_trans *trans,
 	bch2_btree_update_get_open_buckets(as, n);
 	bch2_btree_node_write(c, n, SIX_LOCK_intent, 0);
 
-	bch2_btree_node_free_inmem(trans, path, b);
+	bch2_btree_node_free_inmem(trans, trans->paths + path, b);
 	bch2_btree_node_free_inmem(trans, trans->paths + sib_path, m);
 
-	bch2_trans_node_add(trans, path, n);
+	bch2_trans_node_add(trans, trans->paths + path, n);
 
 	bch2_trans_verify_paths(trans);
 
@@ -1975,7 +1984,7 @@ int bch2_btree_node_rewrite(struct btree_trans *trans,
 
 	if (parent) {
 		bch2_keylist_add(&as->parent_keys, &n->key);
-		ret = bch2_btree_insert_node(as, trans, btree_iter_path(trans, iter),
+		ret = bch2_btree_insert_node(as, trans, iter->path,
 					     parent, &as->parent_keys, flags);
 		if (ret)
 			goto err;
diff --git a/fs/bcachefs/btree_update_interior.h b/fs/bcachefs/btree_update_interior.h
index a6668992a272..adfc62083844 100644
--- a/fs/bcachefs/btree_update_interior.h
+++ b/fs/bcachefs/btree_update_interior.h
@@ -117,16 +117,17 @@ struct btree *__bch2_btree_node_alloc_replacement(struct btree_update *,
 						  struct btree *,
 						  struct bkey_format);
 
-int bch2_btree_split_leaf(struct btree_trans *, struct btree_path *, unsigned);
+int bch2_btree_split_leaf(struct btree_trans *, btree_path_idx_t, unsigned);
 
-int __bch2_foreground_maybe_merge(struct btree_trans *, struct btree_path *,
+int __bch2_foreground_maybe_merge(struct btree_trans *, btree_path_idx_t,
 				  unsigned, unsigned, enum btree_node_sibling);
 
 static inline int bch2_foreground_maybe_merge_sibling(struct btree_trans *trans,
-					struct btree_path *path,
+					btree_path_idx_t path_idx,
 					unsigned level, unsigned flags,
 					enum btree_node_sibling sib)
 {
+	struct btree_path *path = trans->paths + path_idx;
 	struct btree *b;
 
 	EBUG_ON(!btree_node_locked(path, level));
@@ -135,11 +136,11 @@ static inline int bch2_foreground_maybe_merge_sibling(struct btree_trans *trans,
 	if (b->sib_u64s[sib] > trans->c->btree_foreground_merge_threshold)
 		return 0;
 
-	return __bch2_foreground_maybe_merge(trans, path, level, flags, sib);
+	return __bch2_foreground_maybe_merge(trans, path_idx, level, flags, sib);
 }
 
 static inline int bch2_foreground_maybe_merge(struct btree_trans *trans,
-					      struct btree_path *path,
+					      btree_path_idx_t path,
 					      unsigned level,
 					      unsigned flags)
 {